Basket media mill and method

Abstract

A media basket mill is used for dispersing a selected constituent into a liquid vehicle to produce a mixture of the constituent and the liquid vehicle and includes a basket containing a media bed of discrete media elements for immersion within a batch of the constituent and the liquid vehicle in a mixing vessel, a first impellar for establishing a first pressure differential adjacent a first end of the basket for moving the mixture along a circuit through the basket, and through the media bed in the basket, when the basket is immersed in the batch in the vessel and a second impeller for establishing a second pressure differential adjacent a second end of the basket for assisting in the movement of the mixture along the circuit into the basket and through the basket, and through the media bed in the basket, to increase the throughput of the mixture through the basket and the media bed in the basket, while deterring escape of media elements from the basket the second end of the basket.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A media basket mill for dispersing a selected constituent into a liquid vehicle to produce a mixture of the constituent and the liquid vehicle within a mixing vessel, the media basket mill comprising: a basket having an interior and a basket wall including an inner surface and an outer surface, the basket extending axially between a first end and a second end and including an entrance at the second end;   a multiplicity of openings in the basket wall, the openings extending from the inner surface to the outer surface of the basket wall;   a media bed in the interior of the basket, the media bed including discrete media elements, the relative dimensions of the media elements and the openings in the basket wall being such that the media bed is retained within the interior of the basket;   first impeller means for establishing a first pressure differential adjacent the first end of the basket for moving the mixture along a circuit through the basket, and through the media bed in the basket, when the basket is immersed in the mixture in the vessel; and   second impeller means for establishing a second pressure differential adjacent the second end of the basket for assisting in the movement of the mixture along the circuit into the entrance to the basket and through the basket, and through the media bed in the basket, to increase the throughput of the mixture through the basket and the media bed in the basket, while deterring escape of media elements from the basket through the entrance at the second end of the basket.   
     
     
       2. The invention of claim 1 wherein the second pressure differential is less than the first pressure differential. 
     
     
       3. The invention of claim 1 wherein: the first impeller means includes a first impeller having a first overall diameter and being mounted for rotation adjacent the first end of the basket;   the second impeller means includes a second impeller having a second overall diameter and being mounted for rotation adjacent the second end of the basket; and   drive means coupled with the first impeller and the second impeller for rotating the first impeller and the second impeller at the same rotational speed;   the second overall diameter being less than the first overall diameter.   
     
     
       4. The invention of claim 3 wherein the ratio of the second overall diameter to the first overall diameter is approximately 9:16. 
     
     
       5. The invention of claim 1 wherein: the basket is oriented such that the first end is a lower end and the second end is an upper end;   the wall of the basket includes a generally cylindrical side wall extending axially between the first end and the second end of the basket, and a bottom wall spanning the first end;   the openings are located in the side wall and in the bottom wall;   the first impeller means is located at the lower end, adjacent the outer surface of the bottom wall; and   the second impeller means is located at the upper end, adjacent the entrance to the basket.   
     
     
       6. The invention of claim 5 wherein: the basket includes a central axis;   the first impeller means includes a first impeller having a first overall diameter and being mounted for rotation about the central axis adjacent the first end of the basket;   the second impeller means includes a second impeller having a second overall diameter and being mounted for rotation about the central axis adjacent the second end of the basket; and   drive means coupled with the first impeller and the second impeller for rotating the first impeller and the second impeller at the same rotational speed.   
     
     
       7. The invention of claim 6 wherein the second overall diameter is less than the first overall diameter. 
     
     
       8. The invention of claim 6 wherein the ratio of the second overall diameter to the first overall diameter is approximately 9:16. 
     
     
       9. The invention of claim 6 including a plurality of stirring rods mounted for rotation about the central axis, the stirring rods extending radially into the media bed from the central axis toward the side wall of the basket and arrayed axially along the central axis in a spiral, the stirring rods each having a free end spaced radially from and located closely adjacent to the inner surface of the side wall. 
     
     
       10. The invention of claim 9 wherein the discrete media elements comprise beads having a predetermined diameter and the radial spacing between the free end of each stirring rod and the inner surface of the side wall is equal to no more than one and one-half times the predetermined diameter of the beads. 
     
     
       11. The invention of claim 9 wherein the plurality of stirring rods include a lowermost stirring rod spaced axially from and located closely adjacent to the inner surface of the bottom wall of the basket. 
     
     
       12. The invention of claim 11 wherein the discrete media elements comprise beads having a predetermined diameter, the radial spacing between the free end of each stirring rod and the inner surface of the side wall is equal to no more than one and one-half times the predetermined diameter of the beads, and the axial spacing between the lowermost stirring rod and the inner surface of the bottom wall is equal to no more than one and one-half times the predetermined diameter of the beads. 
     
     
       13. The invention of claim 6 wherein the second impeller means includes an axially extending tubular shroud placed around the second impeller such that mixture is moved by the second impeller through the shroud and into the entrance to the basket. 
     
     
       14. The invention of claim 13 including cooling means for cooling the mixture moving through the shroud. 
     
     
       15. The invention of claim 14 wherein the cooling means includes a cooling collar, surrounding the shroud. 
     
     
       16. The method for dispersing a selected constituent into a liquid vehicle to produce a mixture of the constituent and the liquid vehicle within a mixing vessel, the method comprising: immersing a basket containing a media bed within a batch of the constituent and the liquid vehicle in the mixing vessel, the basket having a basket wall, the basket extending axially between a first end and a second end and including an entrance at the second end and a multiplicity of openings in the basket wall;   establishing a first pressure differential adjacent the first end of the basket for moving the mixture along a circuit through the basket, and through the media bed in the basket; and   establishing a second pressure differential adjacent the second end of the basket for assisting in the movement of the mixture along the circuit into the entrance to the basket and through the basket, and through the media bed in the basket, to increase the throughput of the mixture through the basket and the media bed in the basket, while deterring escape of media elements from the basket through the entrance at the second end of the basket.   
     
     
       17. The invention of claim 16 wherein the second pressure differential is less than the first pressure differential. 
     
     
       18. The invention of claim 17 wherein the wall of the basket includes a generally cylindrical side wall extending axially between the first end and the second end of the basket, and a bottom wall spanning the first end, and the openings are located in the side wall and in the bottom wall, the invention including orienting the basket such that the first end is a lower end and the second end is an upper end. 
     
     
       19. A media basket mill for dispersing a selected constituent into a liquid vehicle to produce a mixture of the constituent and the liquid vehicle within a mixing vessel, the media basket mill comprising: a basket having an interior and a basket wall including an inner surface and an outer surface, the basket extending axially between a first end and a second end and including an entrance at the second end;   a multiplicity of openings in the basket wall, the openings extending from the inner surface to the outer surface of the basket wall;   a media bed in the interior of the basket, the media bed including discrete media elements, the relative dimensions of the media elements and the openings in the basket wall being such that the media bed is retained within the interior of the basket;   means for establishing a first pressure differential adjacent the first end of the basket for moving the mixture along a circuit through the basket, and through the media bed in the basket; and   means for establishing a second pressure differential adjacent the second end of the basket for assisting in the movement of the mixture along the circuit into the entrance to the basket and through the basket, and through the media bed in the basket, to increase the throughput of the mixture through the basket and the media bed in the basket, while deterring escape of media elements from the basket through the entrance at the second end of the basket.   
     
     
       20. The invention of claim 19 wherein the second pressure differential is less than the first pressure differential.